1. Field of the Invention
The present invention relates to straddle-type vehicles.
The present application claims priority to Japanese Patent Application No. 2013-108645 filed in Japan on May 23, 2013, the entire contents of which are hereby incorporated by reference.
2. Description of the Related Art
A straddle-type vehicle including an engine in which three cylinders are arranged in alignment with each other in a lateral direction of the vehicle, i.e., a “parallel three cylinder engine”, is conventionally known. JP 2007-83849 A discloses a motorcycle including a parallel three cylinder engine.
The parallel three cylinder engine disclosed in JP 2007-83849 A includes three exhaust pipes in communication with three cylinders. The exhaust pipes are first extended forward and then bent leftward and downward in a front view of the motorcycle so as to be connected to a bundle portion into which the exhaust pipes are collected. A muffler is connected to the bundle portion.
In a parallel three cylinder engine, when an attempt is made to equalize lengths of three exhaust pipes, flexibility of locating the three exhaust pipes is disadvantageously reduced. Besides, the resulting exhaust pipes might unfavorably be complicated in shape. A conceivable solution to these problems is to allow the three exhaust pipes to have different lengths.
However, merely allowing three exhaust pipes to have different lengths causes combustion variations between cylinders, thus making it impossible for a parallel three cylinder engine to deliver its original performance. Another conceivable solution is to devise an engine control method so as to reduce combustion variations, but devising such a method results in complicated control.